Laser therapy is a medical and veterinary technique which uses laser light to stimulate or inhibit cellular function. Recently, this technique has been widely used for treating soft tissue injury, chronic pain, and promoting wound healing for both human and animal targets. The effectiveness of laser therapy is affected by a plurality of factors determined by the properties of the laser light source, e.g. wavelength, power density, energy fluence (dose), pulsing parameters (peak power, repetition rate, duty cycle), as well as by the physical characteristics of the patients, e.g. body-build, weight, gender, skin color, hair color, and body part to be treated, which in turn affects the absorption/scattering coefficient and penetration depth of the laser light in the biological tissue.
Biological tissues are heterogeneous structures, which have spatial variations in their optical properties. The spatial variation and density of these fluctuations make the biological tissue a highly scattering optical medium. A significant fraction of the laser light is scattered multiple times in the tissue, resulting in a low penetration depth. The low penetration depth makes existing laser therapy apparatus extremely inefficient in treating tissues deep below the skin. One way to reach those deep tissues is to increase the power density of the laser light. However, the high laser power may cause overheating and damage the skin tissue (or other superficial tissues). Another approach is to select a longer laser wavelength which is less scattered. However, the laser wavelength that provides the deepest penetration depth may not be the optimum wavelength that produces the best therapeutic effect.
There thus exists a need for an improved laser therapy apparatus and method, which is capable of delivering laser light to tissues deep below the skin for effective therapeutic treatment.